Difluoroamino acetals and method of preparation



United States Patent 3,346,641 DIFLUOROAMINO ACETALS AND METHOD OF PREPARATION Edwin A. Schrnall, Springfield, and John R. Lovett, Edison, N..l., assignors to Esso Research and Engineering Company, a corporation of Delaware N0 Drawing. Filed Aug. 23, 1961, Ser. No. 135,405 Claims. (Cl. 260-584) This invention relates to the reactions of difluoramine (HNF in non-aqueous media with acetals to form new and useful condensation products.

In accordance with the present invention, HNF has been found capable of functioning as a strong acid for replacing an alkoxy group (OR') in acetals, which are represented by the following generalized formula:

wherein R represents H or an organic radical, such as an alkyl radical, an alkenyl radical, or such radicals having substituents which may be alkoxy groups.

The acetals or reactants useful for the desired condensation reactions with HNF are compounds such as the following:

Dimethoxyrnethane HCH(OCH Diethoxymethane HCH OC H Diethoxyethane CH CH(OC H 1, 1,3,3-tetramethoxypropane OCH CH CH CH( OCH Acrolein acetal CH OH CH (OC H Betaethoxy propionaldehyde acetal H C O- CH -CH CH(OC H Acrolein acetal is an example of an acetal having an alkenyl (i.e. ethenyl) or unsaturated R radical and an acetal function, which has two alkoxy groups on the same carbon atom.

For the general conditions of reaction of HNF with 3,340,641 Patented Oct. 10, 1967 tetramethoxypropane was detected by infrared analysis or gas chromatography analysis. Infrared and elemental analysis indicated products having NF groups, in both cuts. The fact that a mixture was obtained suggests that The elemental analysis given in the foregoing table indicates that the ratio of fluorine to nitrogen is of the proper order of magnitude for NF groups replacing an acetal, reaction temperatures in the range of about 20 C. to 200 C., pressures in the range from subatmospheric to 450 p.s.i.a. or higher and reaction periods of about 1 to 100 hours may be used. The reaction period is shortened as the reaction temperature is increased. The reactants are supplied to the reaction zone to form a starting mixture of at least one mole HNF per mole of the acetal reactant and may range up to 1-0 or more moles of HNF per mole of acetal reactant.

To improve contact of the reactants and for safety, various solvents for the HNF may be used as reaction media. Suitable solvents for these purposes are liquid compounds which remain inert or undecomposed and which can be separated from the products. Examples of suitable unreactive solvents are monoglyme, which is the dimethyl ether of ethylene glycol having the formula CH OCH CH OCH tetrahydrofuran, acetic anhydride, sulfuric acid, other unreactive glycol ethers, etc.

HNF has been reacted with a number of different acetals to form condensation products in accordance with the present invention, as illustrated in the following examples:

Example I 1,1,3,3-tetramethoxypropane was reacted with HNF by charging a ratio of 4 moles of HNF per mole of the acetal into a glass bulb reactor under subatmospheric pressure at C. At the end of a period of 65 hours, the resulting liquid product was removed from the reactor and fractionated into 2 cuts, A and B. Gas chromatography indicated three components in each cut, one of the components in each cut being methanol. No unreacted from 1 to about 2 methoxy groups per molecule of the tetramethoxypropane and thereby forming products such as mono (difluoramino) trimethoxypropane and his (difluoramino) diethoxypropane.

Example II Tetramethoxypropane (500 mg, 0.003 mole) was reacted for 3 days at room temperature (23 C.) with HNF (420 mg, 0.008 mole) in one cc. of ethylene glycol dimethyl ether. After pumping off the solvent and unreacted HNF there is attained a good yield of water white liquid on analysis showed replacement of one methoxy group by an NF group. The elemental analysis is tabulated as follows:

Table 2.-Analysis of tetramethoxypropane-HNF reaction product Cale. C H O NF N, 7.5 percent; F, 20.5 percent. Found: N, 6.5 percent; F, 19.8 percent.

Infrared analysis indicated the presence of the C-NF group and thus confirmed the formation of the product mono (difluoramino trimethoxypro pane.

A comparison of the conditions and products obtained in Examples I and 11 indicates that by increasing the temperature, reaction toward replacement of more than one of the alkoxy groups is obtained. Either the monoor bis-difluoramino derivative of the tetramethoxypropane is useful as an energetic component for oxidizing rocket propellant fuel materials, e.g. powdered aluminum, powdered boron, and hydrocarbon moieties. These compounds in having the hydrolyzable alkoxy groups are useful as cross-linking agents or as copolyrnerizing agents.

The reaction of another variety of acetals with HNF is illustrated in the following example:

Example II] 0.35 g. of HNF (6.6 mmoles) was condensed with 0.34 g. of acrolein diethylacetal (2.6 mmoles) in a glass flask. The reactants were then heated to C. for 2 hours. The pressure decrease correspond to a consumption of approximately 2.5 mmoles of HNF A liquid product was isolated by distilling off the excess 'HNF Since a noticeable amount of the acetal apparently polymerized, it appears that at least one mole of HNF had reacted for each mole of acetal. The precise ratio could not be determined. An infrared spectrum of the liquid product indicated NF OH, and a decrease in either groups, compared with acrolein diethylacetal.

The mass spectrum of the gas over the reaction indicated the presence of C H OH. Gas chromatography revealed one major product with a retention time (on silicone substrate) between acrolein diethylacetal and the N F -adduct of acrolein diethylacetal.

Analyses indicated replacement of one alkoxy group Calculated: 1 F, 27.7 percent; N, 10.2 percent. Found: F, 23.9 percent; N, 10.13 percent.

The reaction of this unsaturated acetal with HNF indicates a tendency for the condensation reaction to occur under mild conditions thus forming a product which has a carbon to carbon double bond. The resulting product represented by the formula may be used as a starting material for reaction with N F for addition of NF groups to the double bonded carbons thus providing a higher energy value oxidizer for use as a propellant ingredient.

As shown, the HNF condensation reaction with acetals is particularly useful on acetals containing 3 to about 8 or more carbon atoms to obtain condensation products represented by the formula:

in which OR is an alkoxy group, NF is a difluoramino group attached to the same carbon atom as is (OR), and R is selected from the group consisting of H, alkyl radical, alkenyl radical, and of said radicals having an alkoxy substituent, dialkoxy substituents, and of both alkoXy and difluoramino substituents.

What is claimed:

1. Difiuoramino substituted acetal having the formula:

wherein (OR') is an alkoxy group, NF is a difluoramino group attached to the same carbon as is (OR') and R is selected from the group consisting of H, alkyl radical, alkenyl radical, and said radicals having an alkoxy substituent.

2. Difiuoramino trimcthoxy propane having the formula:

(OCH CH-CH -CH(OCH (NB) 1 For C HdONFz.

3. Bis(difluoramino) dimethoxy propane having the formula:

(NF (OCH )CH-CH 'OH(OCH (NF 4. Difiuoramino ethoXy acrolein having the formula:

H C:CH-CH(OC H (NF 5. Process of substituting an NF group for an alkoxy group (OR') in an acetal having the formula:

wherein R is selected from the group consisting of H, alkyl radical, alkenyl radical, and said radicals having alkoxy substituents, which comprises reacting the acetal with HNF in a reaction mixture containing 1 to 10 moles of HNF per mole of the acetal at a reaction temperature in the range of about 20 to 200 C. under a pressure sub-atmospheric to 450 p.s.i.a. until a product is formed having at least an NF substituted for one of the (OR') groups in the acetal, then recovering as products an alcohol having the composition ROH and the acetal conversion product containing an NF group substituted for at least one (OR') group.

6. The process of claim 5, wherein the reaction of the acetal with the HNF is carried out in the presence of an organic diluent that remains unchanged.

7. The process of claim 5, wherein the reaction is carried out in ethylene glycol dimethyl ether.

8. The process of claim 5, wherein the reaction is carried out in the presence of an unreactive glycol ether.

9. The process of claim 5, in which the acetal is tetrarnethoxypropane having the formula:

(H CO) CH- CH -CH(OCH 2 10. The process of claim 6, in which the acetal is acrolein acetal having the formula:

HgC 2 References Cited UNITED STATES PATENTS 3,310,444 3/1967 Gould et al. 260583 X CHARLES B. PARKER, Primary Examiner.

R. L. CAMPBELL, L. D. ROSDOL, Examiners.

J. W. WHISLER, R. L. RAYMOND,

Assistant Examiners. 

1. DIFLUORAMINO SUBSTITUTED ACETAL HAVING THE FORMULA:
 5. PROCESS OF SUBSTITUTING AN NF2 GROUP FOR AN ALKOXY GROUP (OR'') IN AN ACETAL HAVING THE FORMULA: 